Discharge tube



Aug. 15, 1933. H. FlLlPPO 1,922,672

' DISCHARGE TUBE Filed Nov. 26, 1927 INVENTOR HENDRXCK HUPPO A ORNEY Patented Aug. 15, 1933 UNITED STATES PATENT QFFIcE DISCHARGE v TUBE Application November 26, 1927, Serial No.

235,775, and in the Netherlands January 22,

4 Claims.

The invention is concerned with a process for improving the insulation of the connectors between parts of discharge tubes which during the operation of the tube have a potential difference relatively to one another, and with discharge tubes to which this process has been applied.

It is known that the good functioning of discharge tubes can be harmfully influenced by faults in the insulation of the connectors between parts which during operation have a potential difference relatively to one another. Thus between the lead wires of the electrodes of discharge tubes electric leakages may occur due to the deposit of metal particles, for example, of the magnesium volatilized to obtain a better vacuum in the discharge tube, on the pinch of the stem of the tube between the sealing-in points of the lead wires. The possibility that disturbances in the insulation may occur can be reduced in that case by making the distances between the lead wires or between the points where these wires are sealed into the glass as large as possible, for example, by giving large dimensions to the pinch of the stem. In doing so, however, one is limited to the proportions of the discharge tube so that the result in view cannot always be arrived at.

Now the invention has for its object to suggest a means whereby the said difficulties are overcome in an eflicacious manner.

According to the invention, the process for improving the insulation of the connectors between parts of discharge tubes which during the operation have a potential difference relatively to one another, consists in enlarging the surface of the connectors by providing them with unevennesses. This can be done, for example, by providing the connectors with a rough or granular electrically insulating substance. According to the invention, good results are obtained by providing on the connectors an alkaline earth oxide or an alkaline earth compound which when heated, yields alkaline earth oxide. According to the invention, in order to attain the purpose in view, the connectors may also be provided with an aqueous suspension of calcium carbonate which when heated after being dried, yields the oxide. The calcium oxide thus provided in the tube possesses the favourable property of absorbing any traces of water vapour which may still be present in the tube. The discharge tube according to the invention is provided with other connectors between parts which have during the operation a potential difference relatively to one another, the surface of said connectors being made rough or uneven by being coated with a rough insulating substance.

The invention will be more clearly understood by referring to the accompanying drawing which shows some modes of realization. In this drawing:

Fig. 1 represents on an enlarged scale a stem of a triode adapted to receive a very large filament.

Fig 2 is a mount of a so-called diode.

In Fig. l, 1 is the pinch of the stem of a triode, 4 is a support for the anode, 5 is a lead wire for the grid, 6 are lead wires for the filament, '7 are supports for the filament, 8 is a filament support carrying on its free end a connector 2 of glass or quartz to which the process accord ing to the invention has been applied; The connector 2 carries filament supporting members or hooks 9 which cooperate with the opposite filament supports '7 to hold the filament, 10 is a grid support and 11 is a lead for the anode. The surface of the connector 2 has unevennesses which enlarge its surface in order to prevent leakage or short-circuits. This enlargement of surface can be effected, for example, by making the surface rough in a mechanical way. The same remark applies to the end 3 of the pinch.

In Figure 2 the end surface 3 of the pinch is made rough for the abovementioned purpose. At one end, the filament 13 is secured to leads 17 and 18 and at the other end the filament 13 is secured through spring members 12, 12 to vitreous connectors (glass or quartz beads) 14 and 15 which in their turn are connected to an anode support 16. The anode is indicated at 19.

Due to the deposit of metal particles on the connectors 14 and 15, there may occur a shortcircuit between the filament and the anode of the discharge tube. According to the invention; this undesirable short-circuiting can be avoided by making the surface of the connectors 14 and 15 and the end surface 3 of the pinch uneven.

The process according to the invention will be explained in detail with reference to the stem of a discharge tube represented in Fig. 2. Suppose that one of the alkaline earth carbonates, for example, calcium carbonate is utilized. For this purpose, an aqueous suspension of calcium carbonate is prepared and painted on to the end surface 3 of the pinch and on the connectors 14 and 15. The stem and connectors thus prepared are then dried for about 20 minutes at a temperature 120 0., whereafter the stem is 110 sealed into the bulb of the valve which is then exhausted while heated on the pump to a temperature of 350 to 500 C. During this heat treatment the calcium carbonate decomposes 1 into calcium oxide and carbonic acid. The latport comprising a metal member supported on said stem and another metal member engaging said cathode, and an insulating connector for said metal members having between said metal members a roughened surface of calcium oxide.

2. A discharge tube mount comprising a glass stem, a cathode mounted on said stem, an anode support sealed into said stem, and an insulating connector having a roughened surface of calcium oxide and engaging said anode support and said cathode. Y

3. A discharge tube mount comprising a glass stem, a cathode mounted on said stem, an anode support sealed into said stem, a cathode support comprising a metal member secured to saidanode support and another metal member engaging said cathode, and a vitreous connector for the adjacent ends of said metal member, said connector having a roughened surface of calcium oxide.

4. A discharge tube mount comprising a glass stem, a pair of cathode leads sealed into said stem, a filamentary cathode with its ends secured to said leads, and a cathode support comprising two metal members engaging said filament at points of difierent potential during operation, a

support on said stem for said members, and a vitreous connector between each of said members and said support and having a rough surface of calcium oxide.

HENDRIK FILIPPO.

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